1. Field of the Invention
The present invention relates to a chemical mechanical polishing process. More particularly, the present invention relates to a method of supplying the polishing liquid for the chemical mechanical polishing process.
2. Background of the Invention
Among the very-large-scale-integration (VLSI) or ultra-large-scale-integration (ULSI) manufacturing processes, global planarization can only be achieved by the chemical mechanical polishing (CMP) process. Basically, CMP employs similar concepts of the grinding wheels in conjunction with chemical substances to planarize and flatten the uneven surfaces of the deposited layers over the wafer. Planarization is one of the key factors for achieving high-quality alignment accuracy. If the planarization process goes wrong, it will cause difficulties in focusing for the subsequent photolithographic processes and the misalignment rates may considerably increase.
In addition to the global planarization of the wafer, CMP processes can be applied to fabricate the damascene structures for the vertical or horizontal metal interconnects, the shallow trench isolation structures and to planarize other advanced devices. Furthermore, the planarization process is indispensable for the manufacture of the multi-level metal interconnects.
FIG. 1 is a schematic view of the conventional polishing equipment. The core elements of the equipment 100 are an automated rotating platen 102 and a wafer holder 104. In general, the platen 102 is designed to be a round platen for the convenience of rotation with a polishing pad 106 arranged on the platen 102. A provided wafer 110 is hold by the wafer holder 104 and the position of the wafer holder 104 is adjustable. The wafer holder 104 can both exert force on the wafer 110 and rotate the wafer 110 independent of the rotation of the platen 102. During polishing, the wafer holder 104 ensures the wafer 110 touching the polishing pad 106. A polishing liquid supply 108 is disposed above the platen 102 and provides a polishing liquid 112 for polishing. Polishing of the wafer 110 is accomplished through the polishing pad 106 and the polishing liquid 112. A dresser 114 is usually incorporated in the equipment 100 for conditioning the polishing pad 106.
The choices for different types of the polishing pads or the alterations of the slurry recipes in the polishing processes usually have great impacts on the polishing performance. For the CMP processes, because the used polishing liquid often causes pollution to the environments and needs to be recycled, it is necessary to carefully evaluate the way of using the polishing liquid and the required amount of the polishing liquid.